In particular, the invention relates to a device for detecting the axial position of the rotor shaft of the rotary machine.
There are various types of inductive sensors. Some are based on inductance variation measurements; some are based on eddy currents.
It is known to provide a device for detecting the axial position of the center of a rotor shaft having a target of ferromagnetic material secured at one end of the rotor shaft, an induction coil associated with a stationary magnetic circuit secured to the stator of the rotary machine and placed facing the target while leaving an airgap, and a power supply circuit for powering the induction coil.
Referenced can be made to document EP 2 511 665 which describes a device for detecting the axial position of the center of a rotor shaft comprising a target of ferromagnetic material secured to one end of the rotor shaft.
However, such device is not compatible with a hollow rotor shaft used in application where it is necessary to access the center of the shaft, or at least the center of one end of the rotor shaft. It is also not compatible for application in which the center of the shaft end is used to attach a tool or a turbine wheel.
Furthermore, such device uses a specific target, which increases the cost and the complexity of the detecting device.
In case of a rotor shaft having its center not available, a solution could be to sense the axial position of a shoulder of the rotor shaft, projecting radially towards the stator, or to sense an axial reluctance variation. Such punctual sensing solutions are not satisfactory for large rotor diameter. Furthermore, rotational harmonics may appear on the sensor signal, which may generate vibrations.
The aim of the present invention is to provide a device for detecting the axial position of a rotor shaft shoulder of a rotary machine, without using any specific target.